Regulation of free piston turbo-generator systems



Aug. 8, 1944.

R. PATERAS PESCARA REGULATION OF FREE PISTON TURBO-GENERATOR SYSTEMSFild March '1, 1942 2 Shuts-Sheet 1 loan 6) Ree-5.5025

8404. 847-5646 Pascaea Aug. 8, 1944.

R. PATERAS PESCARA REGULATION OF PISTON TURBO-GENERATOR SYSTEMS 2Sheets-Sheet 2 Filed March 7, 1942 I x3104 1 ,475,645 Pear-4e @zZ U/OAMW5 @florney pier and more eiilcient.

Patented Aug. 8, 1944 "UNITED STATES PATENT j OFFICE REGULATION OI FREEPISTON TURBO- GENEBATOB SYSTEMS Bill Pateras l'escara, llstoril,Portugal, assignor of one-tenth to Societe dEtudes et de Particivpatiom,Geneva,

Eau, Gaz, Electri'cite, Energie, S. A., Switzerland, a society ofSwitzerland Application Mai-ear, 1942, Serial No. 433,805

In France November 4, 1941 I 3Ciaiml- (01.60-13) Thepresent inventionrelates to the regulation of free piston turbo-generator system, that isto'say systems including at least one gas turbine fed with compressedgas by one or several free piston generators.

As it is known, a free piston generator in- I cludes at least onemechanical unit freely movable-in a cylinder an'd'including at least onecomvide a system of this type which is better adapted to meet therequirements of practice'and in particular in which the regulating meansare sim- With thiscbject in view, according to an essential feature ofthe present invention, the system, which includes means for controllingthe amount of fuel fed to the generator or genera- I torsfor'regulatingthe rate of delivery and the pressure of the motor gaseswithin a certain zone of working of the turbine, further includes meansfor acting upon the pressure of themotor gases, by throttling of thepassa e through which they flow, within another zone of working of thesystem.

According to another feature of the invention, I combine, in a singlecontrol member, the

means for adjusting the amount 0! fuel fed to the compressor and themeans for acting directly upon at least one .of the characteristics, forinstance the pressure of the motor gases.

Other features of the present invention will result from the followingdetailed descriptionv of some specific embodiments thereof.

Preferred embodiments of the present inventionwill be hereinafterdescribed, with reference to the accompanying drawings given merely byway'of example and in which:

Fig. 1 is a diagrammatical viewof a power plant including a single gasgenerator and a turbine fed by said generator, together with regulatingmeans according to one form of the invention; v

Fig. 2 is a diagram showing curves of operating values for .the systemof Fig. 1;

Fig. 3 is a diagrammatical view showing the w application of theregulating means of the in- I l supplies compressed air for thescavenging of a .of piston 2, and exhausted into intake manifold ventionto a power plant including a plurality of generators feedinggas to amultiple unit turbine;

; Fig. 4 is a diagram showing curves ofoperating values for the systemillustrated by Fig. 3.

In the following description, the invention is applied to a systemincluding at least one free piston generator and a gas turbine fed bysaid generator or generators.

In the form of Fig. l, the power plant includes a single compressed gasgenerator A feeding gas under pressure to a turbine B, a conduit 0interconnecting the exhaust of the generator and the intake of theturbine, with a reservoir D, mounted'in said conduit and fitted with asafety valve E.

The free piston generator, is of a well known type of construction. Itincludes at least one reciprocating mechanical unit including twopistons I and 2, securedto each other, pisto n I being movable in motorcylinder 3, while piston 2 is movable in compressor cylinderfl.Compressor the motor cylinder 3. Thus air is drawn into cylinder 4through valve-la, on the downstroke to through valve to on the upstrokeof piston 2. Cylinder 3' is provided with inlet ports in and exhaustports 5b. The combustion gases mixed with the excessof the compressedair fed for the scavenging I of cylinder ,3' escape therefrom throughports 5b into conduit C. These gases constitute ,the motor fluid to befed to turbine B. The feed of fuel into the motorcylinder is effected inany suitable manner, for example, as

shown by the drawings, by a device including an injector 6 and a pump 0controlled by rod I operated by a lever s which is actuated by a rod 8'connected to the mechanical unit formed by pistons I and 2 as shown,rod! is carried by piston 2. I

The regulation of the quantity of fuel fed into cylinder 3 can beobtained through the sliding displacement of an adjustment rod 9operated by a regulating device which will be hereinafter described.

In order fully to understand the principle of regulation of such asystem, I will refer to the diagram of Fig. 2 which shows thecharacteristic curves of the rates of delivery plotted in ordinotes,while the pressures are plotted in abscissae. a

In this Fig. 2, therates of delivery are shown:

(a) As relating to the turbine by curve I; and

(b) As relating to the generator by a system of curves ranging withintwo limit curves, one of which, to wit curve II, corresponds to theminimum working stroke of the pistons (necessary for opening thescavenging ports of the motor cylinder), while the other, to wit curveII, corresponds to the maximum stroke which can be achieved'in such amachine.

Curve I intersects curves II and II at two points 112 .and mcorresponding to two different rates of delivery between which thegenerator.

can supply, by suitably determining the length of stroke of itsfreepistons, the amount of gas at pressure suitable for the turbine. Belowpoint m, that is to say for all pressures of admission of gases to theturbinewhich are lower than P2, the generator supplies an excess of gasthat is to say the generator is working at a rate of delivery. higherthan that which is necessary for the feed of the turbine, 'but belowwhich said generator could not work.

Finally, curve III shows the useful powersor loads of the turbine as afunction of the working pressure thereof.

It follows from the preceding explanations that the regulation of thegenerator below point n2 must be different from the regulation at higherpressures.

According to the invention, when, as it is generally the case, thederivative 1 corresponding to curve II in the zone of working below 122,that is to say for loads lower than N2, is negative, the amount of fuelsupplied to the generator is regulated in such manner as to produce theamount 01 gas corresponding to the actual operation of the turbine, thisgas having however a pressure higher than that which corresponds tocurve I. This is imposed by the structure of the generator ascharacterized by curve II, and thus there is interposed in feed conduitC leading to the turbine a throttling member such asa valve III, theposition of which is chosen in accordance with the power to be produced.

This member I reduces for instance, for the desired rate of gas deliveryq, the pressure p of the gases from the generator down to a pressure pwhich corresponds to the rate q of the characteristic curve I of theturbine, when the latter is working with a load equal to N (curve In). I

In the zone of working above point m, that is to say for loads'rangingfrom N: to Na, it sufflces to actmerely upon the amount of fuel injectedintothe motor cylinder.- The regulation is effected either manually orautomatically within the lower and upper limits which depend upon theworking pressure of the generator and correspond to the minimum andmaximum strokes, respectively, of the generator.

In the example shown by Fig; 1,' rod 9, which determines the amount offuel fed to, cylinder 3, h

is controlled by a lever II pivotally connected-at II. to said rod. Thedisplacements of rod 9 are limited'by a cam I2 including two inclinedsurfaces adapted to cooperate with a finger 9" carried by a rod 9';pivoted to control rod 9. The action of cam I2 must be variable inaccordance with the value of the working pressure of the generator. Forthis reason, in the example illustrated by Fig. 1, rod 9', which carriesfinger .9", is mechanically connected with a piston I3 one of the facesof which is subjected to said working pressure, fed through conduit I4,

It will be readily understood that, with such an arrangement, it ispossible, for every working pressure, to vary the amount of fuel whichdetermines the rate of delivery of the motor gases, within two limitswhich are variable in accordance with the value of said workingrpressure.

' As it results from the shape of characteristic curves II and 11 shownby the diagram of Fig. 2, the shape of the inclined surfaces of cam I2is such that the limits of abutment are closer to each other as thepressure is lower.

According to another feature of the present invention, the tworegulating means 9 and III, which act respectively for workingconditions below and above m, are combined together so as to be operatedby a single control member operated either manually or automatically bythe speed governor of the turbine.

- I For this purpose, supposing that throttling zone of loads for whicha throttling of the gaseous stream is efiected and, on the contrary, camIE must not work within the zone of loads for which regulation isobtained merely by quantitative variation of the fuel fed to cylinder 3.

This result can be obtained in various ways. For instance, as shown byFigure l, lever I I pivots about an axis I Ib, carried by twoopposed-springs 29 and 20. On the other hand, cam I6 is given a circularoutline beyond the position for which the throttling member I0 is fullyopened.

Finally I provide safety means for reducing or even stopping the feed offuel to the motor cylinder when the point m (pressure pa) ofcharacteristic curve I is reached. This device includes a pistonoperated on the one hand by the working pressure of the generator andsubjected on the other hand to the thrust of an opposing spring 9|.Piston 90 is joined in a rod 92 which will force finger 9 against theinclined face of cam I2 which corresponds to the minimum rate ofdelivery of the generator, when pressure p: is exceeded. g

The working of the regulating system according to the invention, asabove described, is the following: a

After the system has been started, throttle valve I II is first fullyclosed. The pressure increases-in reservoir D up to a value 101 corre-'sponding to a rate of delivery Q1 of the generator.

Ifthrottle valve III is not immediately opened, the gases fed by thegenerator escape to the outside throughsafety. valve E.

For the positions of control member III which corresponds to a full orpart closing of throttle valve III, the tension of springs 20, 20'applies finger 9" against the inclined face of cam I2 which corresponds,for the various pressures that may exist, to the minimum rate ofdelivery of the generator.

' When operating member I9 is moved in the direction of the arrow markedby the positive sign, throttle valve I0 is gradually opened, while thelever II pivots around pivot Na and therefore has no action whateverupon rod -9. The inlet pressure of the gases fed to the turbineincreases at the same time as the generator delivery preasuredecreases.

If, for instance, the power required by turbine B is equal to N, saidturbine must be fed with an amount q of gas of a pressure equal to P.

On the other hand, in order to'obtain this amount q of gas from thegenerator, the latter must work-at a pressure equal to P as this resultsfrom the curve II of. Fig. 2. 'I'herefore, throttle valve III is openedin such manner astoreduce the pressure P existing in reservoir D,down-to the pressure P at which the motor gases enter turbine B. Due tothe action of piston I3, the-position of abutment of finger 9" upon theinclined face of cam I2 which corresponds to the minimum stroke ofpistons I2', varies as a motion of the pressure when the latter varies.between P1 andlz. The amount of fuel fed dur- .ing this period thusensures, for every given delivery pressure, a minimum stroke of thegenerator. This situation is maintained until throttle valve I is fullyopened, which corresponds to power N: (Fig. 2) and pressure P2.

For powers ranging between N: and N3, finger l" is no longer compelled,by springs ill and 29', to bear,against that of the two inclined facesof cam I2 which corresponds to the minimum stroke, said springsnowkeeping the pivot point III: of lever II in a substantially fixedposition.

The action of lever I9 is then directly transmit ted, through lever II,to the fuel feed regulating rod 9 whereby the rate of delivery of thegenerator is varied within limits determined by the inclined faces,acting as abutments, of cam l2 1 which correspond respectively to theminimum and maximum strokes of the generator. As above explained,,-theseabutments depend upon the'action of the working pressure of thegenerator, said pressure being practically equal to the pressure ofadmission to the turbine when the throttle valve is fully opened andincreasing simultaneously with the useful-power.

. amount of fuel fed to each of the generators A1,

During thewhole of this regulation period, the

throttle valve remains open due to the circular shape of thecorresponding portion of cam I9.

I will now describe a regulating system according to the invention whenthere are'several generators and eventually several turbines.

This form is iliustratediby Fig. 3. It corre- I sponds to the case ofthree generators, A1, A2, As, and three turbine elements working on thesame shaft. For instance, element Bp constitutes the main turbine,element Bc constitutes the turbine to be used for reduced power working,and element B1- is the turbine to be used'for backward operation;

Thesethree turbines, fed through a common II: and II: are thecharacteristic curves of the rate ofdelivery as a functionpf thepressure for three generators, for the minimum stroke and themaximum'stroke respectively.

I will designate by the expression throttling regulation the regulationabove described ac.- cording to which the control member actssimultaneously upon the throttling member In and upon the means forregulating the fuel feed.

The expression free control pump delivery regulationdesignates theregulation for which, the throttling means being fullyopened,'thecontrol member acts, within limits determined by the inclinedsurfaces of the cam, upon rods 91, 9: and 93 which control the fuel feedto the generators.

It results from Fig. 4 that the second mentioned regulation system isapplicable: I

(a) For turbine Bp, and three generators, within zone -tpup;

(b) For turbine B1, and two generators, within- 'in the case of a singlegenerator, each generator is fitted with its regulating system byconnecting the rods 91, 92, 93, which determine the 'A2, A3, with-alever 9'1, 9'2, 9'3 subjected, on the one hand, to the action of apiston I31, I31, I31, one of the faces of which supports the dischargepressure of the corresponding generator, and, on the other hand, to theaction of a pivoting lever H1, H1, Ila. I further provide cams I21, I21,I33 having two inclined surfaces acting-as 'abutment's for limiting thedisplacements of each of the groups 91-.9'1, 9z-92, 9a--9'3.Furthermore, I connect the free ends of levers H1, 2, II: with a singlered I8 by springs 20 and 20' operated by a single control-member I9.Lever I9 is operatively connected with a link system capable ofcontrolling throttling member IIl'through conduit C, have each theirdistinct ,inlet whiletheir outlet 30 is common to the three of them.

' Valve means V1, V1 and Va permit the independent feeding. of gas tothe respective turbine elements. 1

Check valves such as 301, 30: and '90: are

I between conduit C on the one hand and,

the other hand, reservoirs D1, D2, D3, respectively fed by generatorsA1, A: and As.

, In the diagrams of Fig. 4:

I, is the characteristic curve giving the rate of flow as a function ofthe pressure in turbine Bp;

I: is the characteristic curve giving the rate of flow as a function ofthe pressure in turbine B1: In is the characteristic curve givingthe'rate of fiow as a function of the pressure in turbine Be; 111 andII1 are the characteristic curves ofthe rate of delivery as a functionof the pressure for a cam I6 which includes, as above explained, acircular portion whereby lever I9 ceases to have any action upon memberI0 after said member has been fully opened, Lever I9 may be manuallyoperated or it may be coupled with the governor 2i of the turbine.Throttlingmember' I0 is located'in conduit C which is common to thethree generators, whereby it sufilces to provide a single throttlingmember.

Concerning now the operation at rates of delivery respectively lowerthan those of points.

in, t1- and is, the desired result is obtained by producing, in a mannersimilar to that above explained, a drop of pressure in the feed conduitC of the turbine through the operation of throttling member I0.

As long as this member I0 is not fully opened, pumps 61, 6: and 6a areworking at their minimum rate as is permitted by pressure exigencies inthe generators, due to the opposed action of springs 20, 20 and of thecorresponding pistons I31, I32, I33, these spring actions causing therespective rods 9'1, 9'1 and 9: to bear against generator,

4 o the inclinedsurfaces of cams *m, 12, m m which correspond to minimumrate or, delivery.

Theplant illustrated by Fig. 3 can also be used for feeding a singleturbine. such for instance as turbine 'Bp, according to the loadthereof, through one, two, or three generators. Ifor this purpose, Iprovide means for varying the length of rod I8. Such means may forinstance consist of a threaded part 40 carried by one section of rod 18and cooperating with a threaded socket, 4i carried by another section ofsaid rod.

By thus varying the length of said rod, it is possible to cause-turbineB to work between point tp and up (Figure 4) when three generators arein operation, between points s and p when two generators are inoperation, andv between points n and m, when a single generator is inoperation.

The variation of length of rod l8 correspondingto the three differentways of operating is chosen in such manner that for the same position ofhand lever I 9, corresponding to full opening of throttle valve Ill, theadjusting rod of the various injection pumps is just being released bythe cam determining minimum injection, for

. pressures which are the lower as the number of generators in operationis smaller.

Supposing that, a certain number of generators being already in action,it is desired to bring a new generator, for instance A1, into action, itwill be noted that as long as the delivery pressure of this new machineis lower than the pressure,

inconduit C, the action of springs 20, 20', com

bined'with the action of the corresponding piston I31, produces thevfeed of fuel which corresponds to the operation of the apparatusindependently of the turbine, for instance byinjecting the maximumamount of fuel that is admissible in view of the pressure conditions. Assoon as apparatus A1 feeds gases through conduit C, due to the openingof check valve jectedto the same actions as the regulators of thegenerators which were already in action and all the apparatus that areworking, including the newone, are regulated in the same manner, theirregulating means-being subjected to the same actions.

In a general manner, while I have disclosed I what I deem "to beeilicient and practical embodiments of the present invention, it must bewell understood that I do not wish to be limited thereto as there mightbe changes made in the 301, the regulator of the new generator issubform, dimensions and dispositions of the part; without departing fromthe principle of the invention as comprehended within the scope of theappended claims.

What I claim is:

1. In the combination of a free piston generator, a turbine, a conduitconnecting the exhaust of said generator with the intake of saidturbine, a throttle in said conduit, and'fuel feed means for saidgenerator, the improvement comprising means for limiting the rate offuel feed by said feed means, means responsive to the exhaust gaspressure of said generator for varying said limiting means, a singlecontrol means. means connecting said control means with said responsivemeans and means connecting said control means with said throttle, atleast one of said connecting means including a resiliently supportedpivot and lever articulated to said pivot,

